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Confidence in Scientific Knowledge

by Jeff Lewis

In a similar vein to the preceding essay, while this topic isnít exactly religious, many religious people do reject science because of their faith, so I thought it was fitting to include it here.

I tend to place a lot of value in science. I think it's the best method we have for answering questions with objectively true answers, and I think we can have a pretty high confidence in the answers it gives us. But, as several people have asked me, where does that confidence come from? Throughout the past, people have had explanations for aspects of the universe that they believed were correct, but have since turned out to be wrong (e.g. the Sun orbiting the Earth). Given humanity's history of failed explanations, shouldn't we expect that many of our current explanations are also wrong, and be a little more cautious in our certainty?

The simplest reason to be confident in science is a pragmatic one - just look at the results. Science as the formalized discipline that we're used to is a fairly recent development. It's only been around a few hundred years, getting started in the Renaissance, but not really coming into its own until after the Enlightenment [1]. But look at how fast our technology has progressed in that short time compared to the previous millennia of human existence. We've invented telescopes, steam engines, automobiles, semiconductors, airplanes, computers, TVs, radio, lasers, vaccines, antibiotics, cures for some cancers. We've sent people to the moon. These accomplishments are all based on knowledge that we've learned through science. It seems very unlikely that we would have been able to accomplish all of that if we didn't have a pretty accurate understanding of reality. Granted, there are other fields of science that haven't yielded practical applications, and possibly never will. For example, understanding the Big Bang may not ever give us any new technologies. However, given the technologies we have developed from other fields, we know that the methods produce reliable results.

Moving away from pragmatism, let's look at how science works. Richard Feynman once said, "Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool." There are all types of ways that we can make mistakes in our reasoning. There's a great article from the Winter 2005 issue of Skeptic Magazine that I would encourage everybody to read, The Double-Blind Gaze: How the Double-Blind Experimental Protocol Changed Science [2]. The article is focused on medicine, but it's applicable to science in general. The article mentions a few of the confounding factors that can affect our reasoning, including the placebo effect, the re-interpretation effect, and observer bias. One can find long lists of cognitive biases from sources such as Wikipedia [3]. A big part of science is recognizing and accounting for all these potential mistakes. Along similar lines, science is not just a search for evidence that confirms your ideas. It's a search for evidence that would disprove your ideas. A big part of science is recognizing when you're wrong.

Science also trains us to think less in terms of absolute certainty, and more in terms of degrees of certainty. If you're being honest with yourself, there's no way to be absolutely certain of anything. It's possible that we're living in The Matrix, or hallucinating, and nothing is as it seems. In normal everyday conversation however, we tend to ignore those types of outlandish possibilities, and say that we're positive of something, even if technically we mean nearly positive. There are many things we've learned through science that, using everyday language, we can say we're positive are true. The roughly spherical shape of the Earth, the Earth orbiting the Sun, common descent (if not all the exact lineages and mechanisms), are examples of a few of those facts. We should no sooner expect those facts to be overturned than we should expect to wake up on the Nebuchadnezzar fighting alongside Neo [4]. Other things we've learned through science don't have quite as much evidence. Anthropogenic global warming is an example of this. We can say that we're really darned sure that climate change is happening and that we're responsible, but it's not quite so certain. It would still be really surprising to see AGW turn out to be false, but not earth shattering. You can keep moving down through levels of certainty through things like String Theory, which doesn't really have any evidence confirming it specifically over other theories, but which is at least consistent with known evidence. If string theory turned out to be false, I wouldn't be all that surprised. You can go even further, and find theories inconsistent with known evidence, such as the supposed link between vaccines and autism, or the aether theory of light. We can be pretty sure that those ideas are false.

In addition to making us think in terms of degree of certainty, science also makes us think in terms of degree of accuracy. Isaac Asimov wrote a good essay titled, The Relativity of Wrong [5]. Readers are encouraged to read the entire thing, but here's a great quote from that essay, "When people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together. [6]" An example I've used before is the atom. The current model is the valence shell model, where electrons have a probability of being in particular positions relative to the nucleus. This is an improvement over the Bohr model, where electrons travel in circular orbits around the nucleus and where the orbit radii are defined by quantum mechanics. The Bohr model was an improvement over the Rutherford model (or Solar System model), where the electrons orbited the nucleus, but quantum mechanics wasn't incorporated to predict the orbit radii. The Rutherford model was an improvement over the plum pudding model. And the plum pudding model was at least more accurate than not knowing of the existence of electrons. So, you can see how our explanations have gotten more and more accurate concerning the structure of an atom. Our current model may also be supplanted, but at least we're zeroing in on the truth.

Those are the reasons why we can have confidence in what we learn through science. It's produced results that just wouldn't be possible if the methods didn't work. But it's not simply a matter of thinking that everything science reveals is absolutely right - it's recognizing how science works, what explanations are most likely to be true, and how close we should expect those explanations to be to the actual truth.





[4] For those who havenít watched the movie, this is another Matrix reference.


[6] Even if you ignore the deviations from a perfect sphere due to mountains, valleys, and other such features, there is a slight bulge due to the spin of the Earth thatís greatest at the equator, making the shape closer to an oblate spheroid than to a sphere. There are also the tidal forces caused by the gravity of the sun and moon, which distort the Earth further (a bit like a football, but not nearly so extreme). Still, these distortions are fairly minor.